The document provides examples of using addition and subtraction to find unknown numbers represented by variables in mathematical equations. It shows how to cover numbers in an equation with your finger and use the other numbers and operations to determine the hidden value. Several practice problems are included with letters representing unknown numbers and equations to solve for the value of the variable.

1. lesson 3.notebook August 24, 2012
Lesson 3: Do not write this out!!
*Cover the 6 with your finger. How can you use the 11 & 5 to find
that the number under your finger is 6?
6
+5
11
*Cover the 11 with your finger. How can you use the 8 & 3 to find
that the number under your finger is 11?
11
- 8
3
1

2. lesson 3.notebook August 24, 2012
*equation - a statement that uses the symbol "=" to show that
2 quantities are equal
*unknown number (variable) - a value that is not given
...typically a letter is used
n + 24 = 95
2

3. lesson 3.notebook August 24, 2012
Lesson 3 Examples:
Find the unknown number in each problem.
A) A
+ 12
45
B) 32
+ B
60
3

4. lesson 3.notebook August 24, 2012
C) C
- 15
24
D) 38
- D
29
4

5. lesson 3.notebook August 24, 2012
E) 36 + 14 + g + 8 = 75
5